Growing pressure on pesticide use has put integrated pest management (IPM) at the centre of regenerative and sustainable agriculture.
That pressure comes from several sources, including consumer concern, which has led to more stringent environmental regulations and removal of products from the marketplace. There are also fewer new pesticides in the pipeline to replace them, with no entirely new chemistry on the horizon. Worse still, pest resistance to certain active ingredients has rendered other products ineffective.
The long-term outlook then, points to using chemical controls with care, ideally as a last resort, within a wider IPM strategy.
Most conventional growers already employ at least some IPM techniques like pest-resistant crop varieties and diverse rotations. But researchers are now urging conventional growers to boost natural pest control using beneficial invertebrates. While growers may think this will reduce yields there is growing evidence, based on practical research, suggesting otherwise.
Researchers from the UK Centre for Ecology & Hydrology (UKCEH) and Rothamsted Research have been working with farmers to increase populations of crop pest predators in the centre of large arable fields. This work is part of a large, government-funded programme called Achieving Sustainable Agricultural Systems (ASSIST).
Professor Richard Pywell, head of biodiversity research at UKCEH, explains that agricultural ecosystems used to rely on thriving populations of predatory insects to help control pest species. “More efficient farming methods have caused the loss of wildlife habitats, like hedgerows, scrub, trees, and wildflower meadows,” he says.
loss of beneficial species
Modern agricultural practices have caused a decline of crop pollinating insects, aphid-killing ladybirds and spiders, along with ground beetles which previously attacked slugs and other larvae.
Beneath the soil, worm populations which had improved the fertility and structure, drainage and workability of land, have been reduced by pesticides, over-cultivation and a lack of organic matter. “The loss of these beneficial species has added to the over-reliance on pesticides and fertilisers required to maintain yields,” says Prof Pywell.
However, research has demonstrated that restoring habitats rich in certain wildflowers that encourage these species can help redress the situation, relatively quickly.
And the creation of wildlife habitat doesn’t have to be detrimental to profit margins. Virtually all farms have low-yielding or awkward areas, including headlands, in-field pylons and trees. Removing these areas from production to create wildlife habitat can actually increase overall profitability.
These areas could be used to create wildflower and grass strips which would provide habitats for pest predators like ground beetles, spiders, parasitic wasps, parasitoids, lacewings and ladybirds. They will also benefit crucial pollinators.
“But, while many growers already drill field edges with wildflower seed mixes under stewardship agreements, there is a need to go further,” Prof Pywell says. The benefits of natural pest control provided by predatory insects diminish rapidly 50m from the flower-rich field margins, so the crop centre can still become a pest haven.
To tackle this issue ASSIST has trialled wildflower strips in field centres to maximise natural pest control. The strips work within farm operations, fitting in with tramlines and drilling, and are not connected to the headland. This allows efficient farming around the end of strips and avoids adding awkward corners to the field.
As well as in-field flower strips, other techniques are being evaluated including establishing oilseed rape in long cereal stubbles and sowing companion crops like buckwheat and berseem clover. Together these show promise in reducing damage to the crop cause by cabbage stem flea beetle.
“Conventional farmers can also benefit from soil and nutrient management practices developed by organic farmers,” says Prof Pywell. Establishing herbal leys rich in nitrogen-fixing legumes in the rotation increases organic matter, boosts soil nitrogen and provides flowers for crop pollinators and other beneficial insects. Worm populations thrive and draw down organic matter in a process that aerates soil and improves structure, leading to both better moisture retention and drainage.
“The combination means crops are less prone to drought stress while being better able to support traffic, allowing fieldwork to be carried out in a more timely manner.”
Flower rich strips
- At least 6m wide
- Three boom width separation (96-108m) to fit tramlines
- Drill late August
- Mow to reduce weed species
- Seed mix
- 4 kg/ha wildflowers
- 10 kg/ha of grasses
- Flower species: Wild carrot, yarrow, oxeye daisy
- Clovers: Birdsfoot trefoil and red clover
- Tall grasses: Cocksfoot at strip edge for ground predators and protection for the flower-rich core.
Arable grower Tom Sewell has adopted organic farming and no-till techniques with huge success. Sewell Farms is a family-run partnership, managing about 567ha in the Medway Valley, Kent, for 15 landowners under various tenures. It also owns a small proportion of land.
The land has not needed any insecticide for four years and no seed treatments have been used for the past two growing seasons. Despite the lack of chemical inputs, wheat yields are between 10t and 12t/ha. Mr Sewell, a former Nuffield Scholar who studied regenerative and no-till practices in 2013, says the farm’s strategy began by questioning every long-held, routine method used. As a result of that review, all non-essential cultivations have been cut out. There are no second wheats, with a break crop always following in the rotation – which also includes barley, oats, beans and grassland. Variety choice is pivotal to the strategy with Extase winter wheat chosen for its good disease-resistance properties and its high-yielding characteristics.
Mr Sewell uses compost from soft fruit farms, rather than bagged fertiliser, with companion and cover crops helping to boost soil fertility and reduce weed species. He routinely monitors soil nutrients to ensure he only applies what the soil needs. Because of this he hasn’t used any bagged P or K for almost 20 years.
Liquid nitrogen applications are minimised because Mr Sewell says the stimmulated growth leads to thinner, weaker cell walls in the plant, increasing its vulnerability to pest and disease attacks.
He chops straw stubble and sprays off any volunteers within 24 hours of drilling, ensuring cover is maintained up to the last moment. A developing technique is to leave the stubble about a foot high, which has important benefits. Firstly, the long stubble provides a break from the wind, which would otherwise dry out the surface and result in erosion. It also helps retain moisture at the soil surface.
In a way we have become livestock farmers, producing insects above ground and worms beneath the soil surface.
“Even during dry periods there is moisture in the soil helping to maintain its structure – which is tilthy and crumbly,” says Mr Sewell.
The third crucial benefit is to act as a haven for insects across the whole field. The result has been spectacular. “In the mornings the field surfaces are silver with dew on the webs of wolf spiders,” Mr Sewell says. The spiders then take out the aphids, keeping numbers below spray thresholds.
“In a way we have become livestock farmers, producing insects above ground and worms beneath the soil surface,” he says. “Ground beetles tackle the slugs and larvae in the soil so that we no longer have any problem with these, removing the need for seed treatments.”
A recent worm count revealed a staggering 12 million worms per hectare. “The worms do a fantastic job for us by dragging organic matter deeper into the soil and recycling nutrients. Their action benefits soil stability and structure so that while soil is free-draining and provides a solid base for drilling, it retains moisture in the organic matter,” he explains.
Despite the lack of chemicals on the farm, glyphosate is used once a year to provide a clean slate for the crops to go in. “We need to retain certain chemicals for the future and that is another good reason for using them so sparingly,” Mr Sewell says. And using as little as possible benefits the bank balance, too.
UKCEH has recently released a free, web-based tool called the E-Planner which maps the suitability of every field across Great Britain for the creation of a range of wildlife habitats, including wildflowers, wild bird food, buffer strips and woodland. Farmers can then use the free UKCEH phone app called E-Surveyor to easily assess how successful habitat creation has been. The app uses image recognition technology to identify the plant species and compare them to the seed mix.